The invention relates to a tension bar for transmitting tensile forces, and more particularly to a lifting bar or upper steering arm of a three-point attaching device of tractor. The bar is attached to the attaching points of the parts to be connected. The bar includes attaching ends with the tension axis of the tension bar extending through its center.
Many agricultural implements are designed to be attached to a tractor. In particular, light soil working equipment such as harrows, rotary cultivators and implements distributing fertilizer and seeds such as fertilizer distributors and sowing machines are types of implements attached to tractors. It is common practice to functionally connect these tractor implements to the tractor via a three-point attaching device. The device includes an upper steering arm and a lower steering arm. In the case of tractor implements which do not come into contact with the soil and which supply the soil with substances, such as fertilizer distributors and sowing machines, it is insufficient, for operational and environmental reasons, to distribute the load of substances or materials from the driver's seat with the help of a preselected setting. In these cases, it is important for such substances or materials to be accurately metered. Such metering is permitted by continuously determining the weight of the loaded implement. Thus, at any time, even and especially when negotiating agricultural land, the weight loss resulting from the distribution of substances can be determined.
In the case of heavy implements carried by the three-point attaching device at the tractor rear, the load on the front axle is reduced, which, when operating a four-wheel drive, leads to a reduction in the contribution to traction made by the front wheels. Devices are know which determine the weight of tractor implements loaded with goods, also referred to as tractor scales.
DE 35 39 825 C2, published Jun. 8, 1989, provides frame structures arranged between the three-point attaching device of the tractor and the implement. The frame structure includes a load frame and a carrier frame connected together by a spring suspension which includes a pressure sensor to determine the weight of the implement.
DE 39 23 198 A1, published Jan. 24, 1991, describes tractor scales which also include a frame structure and which are arranged between the three-point attaching device and the tractor implement. These proposals are disadvantageous because the additional structure increases the weight of the complete tractor/implement system and changes the implement kinematics, which compensation for is expensive, and increase the maintenance expenditure.
DE 38 20 757 A1, published Dec. 28, 1989, discloses combining an electro-hydraulic lifting and control system of a tractor with a device to determine the weight of the attached loads, such as tractor implements loaded with goods, without using an additional frame structure arranged between the three-point attaching device and the tractor implement. By locating sensors in carefully selected regions in a control device, it is possible to obtain both load and position dependent signals which allow the weight to be determined via an electronic evaluating unit.
Incorporating the electro-hydraulic lifting and control device in the weight determining system causes several problems. One problem with pure pressure measurements is that a complicated electron system is required due to the fact that it becomes necessary to take into account the compensation of static and hydraulic interfering influences and the relatively high hysteresis. Integrating the system weight determining system into the existing electron-dynamic lifting system does not enable the weight to be determined independently of the system. Any problems which might arise in the hydraulic system always lead to disturb the weight determining process. Furthermore, a weight determining process which is independent of the center of gravity and lifting height, which is very largely possible, requires a more sophisticated technical and electronic system. All the electronic facilities are at risk, especially with respect to their functioning, if the implement received by the three-point attaching device, in the lifted position, required for transport is subject to uneven tracks and roads which cause impacts which greatly exceed standard operational loads.